Method of diagnosing renal diseases

Abstract

A method of diagnosing renal diseases by detecting fragments of albumin in human urine. The detection of the fragments is carried out by, for example, immunological methods or liquid chromatography techniques.

What is claimed is: 
     
       1. A method of diagnosing diabetic or IgA nephropathy of an early stage comprising: (a) obtaining a urine sample of a patient suspected of being at an early stage of nephropathy, which urine sample does not contain sufficient microalbumin to obtain a positive result in a microalbumin test;   (b) separating all of the proteins contained in the urine sample or immunologically recovering albumin and albumin fragments from the urine sample;   (c) testing the sample from (b) for the presence of albumin fragments by immunologically identifying albumin fragments in the separated proteins or by chromatographically identifying any recovered albumin fragments; and   (d) detecting the presence of albumin fragments in the sample, wherein the detection of albumin fragments is indicative of an early stage of nephropathy.   
     
     
       2. The method of claim 1, wherein the test for the presence of the albumin fragments comprises immunologically identifying albumin fragments and electrophoresis. 
     
     
       3. The method of claim 2, wherein the immunological technique is selected from the group consisting of immunoassay and immunoblot. 
     
     
       4. The method of claim 3, wherein the immunological technique is immunoblot. 
     
     
       5. The method of claim 2, wherein the electrophoresis is SDS-polyacrylamide gel electrophoresis (SDS-PAGE). 
     
     
       6. The method of claim 2, wherein the electrophoresis is cellulose acetate electrophoresis. 
     
     
       7. The method of claim 2, wherein the electrophoresis is electrofocusing. 
     
     
       8. The method of claim 4, wherein the immunological test for the presence of the albumin fragments comprises separating all of the proteins including the albumin fragments from a urinary sample by SDS-PAGE or electrofocusing, transferring the proteins in the gel to a transfer support, incubating the support with anti-human albumin antibodies as first antibodies, incubating the support with enzyme-labeled anti-IgG antibodies as second antibodies and staining the support with an enzyme-detection reagent. 
     
     
       9. The method of claim 4, wherein the immunological test for the presence of the albumin fragments comprises separating all of the proteins including the albumin fragments from a urinary sample on a cellulose acetate sheet by electrophoresis, transferring the proteins on the sheet to a transfer sheet, incubating the support with anti-human albumin antibodies as first antibodies, incubating the support with biotinylated anti-IgG antibodies as second antibodies, incubating the support with enzyme-labeled avidin and staining the support with an enzyme-detection reagent. 
     
     
       10. The method of claim 3, wherein the immunological test for the presence of the albumin fragments comprises separating all of the proteins including the albumin fragments from a urinary sample on a cellulose acetate sheet by electrophoresis, directly immobilizing the proteins on the sheet, incubating the sheet with anti-human albumin antibodies as first antibodies, incubating the sheet with bioinylated anti-IgG antibodies as second antibodies, incubating the sheet with enzyme-labeled avidin and staining the support with an enzyme-detection reagent. 
     
     
       11. The method of claim 1, wherein the test for the presence of the albumin fragments comprises liquid chromatography. 
     
     
       12. The method of claim 11, wherein the test for the presence of the albumin fragments comprises gel filtration chromatography or ion exchange chromatography. 
     
     
       13. The method of claim 12, wherein the gel filtration chromatography or the ion exchange chromatography is high performance liquid chromatography. 
     
     
       14. The method of claim 12, wherein the native albumin and the fragments thereof are purified by affinity chromatography before they are detected by the gel filtration chromatography or the ion exchange chromatography. 
     
     
       15. The method of claim 14, wherein anti-human albumin antibodies are used as ligands of the affinity chromatography. 
     
     
       16. The method of claim 12, wherein the support for the gel filtration chromatography or the ion exchange chromatography is selected from those used for separation and analysis of proteins. 
     
     
       17. The method of claim 1, wherein the nephropathy diagnosed is diabetic nephropathy. 
     
     
       18. The method of claim 17, wherein the urine sample is obtained from a patient having diabetic mellitus. 
     
     
       19. The method of claim 1, wherein the nephropathy diagnosed is IgA nephropathy.